Do you really need an air ride hitch
DO YOU REALLY NEED AN AIR RIDE HITCH?
All of us that have an air suspension hitch know the value of it. However, I still have people who have a solid mount hitch telling me they do not have any problems with how their 5th wheel RV rides. I'm not sure they know if they do or not. Just because the TV stays in place does not necessarily mean they do not have problems but don't know it. In talking about the suspension systems you hear words like inertia, mass, sine waves, kinetic energy, etc. We are taking a simple problem that has been around since there have been trucks and making it much more complicated than it really is. There is ONE word to describe why we need additional suspension for our 5th wheel. It's BUMP! As in 1. To strike or collide with. 2. To cause to knock against an obstacle. BUMP is also known as Kinetic Energy. If we look at the suspension system on the MDT we can see why it rides rougher than a pickup truck.
Lets look first at the suspension on a pickup truck. Its suspension
from the factory is leaf or coil springs and shock absorbers. When we hit
a BUMP the tire is the first thing to make contact. The tire in itself, if
properly inflated, will absorb approximately 25% of the BUMP, but what is
not absorbed by the tire is transmitted to the springs and shock
absorbers. The springs bend to dissipate the BUMP and the shocks move in
conjunction with the springs to dampen the movement of the springs and also
absorb some of the BUMP. If the BUMP is so big as to when the tires,
springs, and shocks can't absorb it, then the remainder of the BUMP is
transmitted into the frame of the vehicle, which absorbs the remainder of the
BUMP. However, when this happens, the portion of the BUMP that is
transmitted into the frame of the vehicle is called stress and fatigue.
The suspension system on light duty vehicles is designed for a given weight
load. This load usually will not vary more than 500-1200 pounds.
Given that factor, the suspension is designed to absorb most all of the BUMPS
the vehicle comes in contact with, making for a smooth ride most all of the time
in most all conditions. A factor, which is often overlooked, is the weight ratio
between the pickup and the trailer it is pulling. When the trailer grossly
outweighs the pickup there will be adverse effects on the ride of the pickup.
When the trailer tires come in contact with a BUMP that is large enough so that
the trailer suspension cannot dissipate the energy, it is transferred to the bed
of the pickup via the connection of the stationary hitch. This energy is then
dissipated in the jerking action felt in the truck. When a separate suspension
system is installed in the bed of the truck (an air ride hitch) the energy from
the bump is now dissipated in the movement of the hitch through the air springs
in the hitch. By using an air ride hitch most all of the jerking action is
removed from the ride in the truck.
Medium and Heavy Duty Trucks on the other hand have a completely different
design in their suspension system. It is mandatory to maintain a proper
height between the frame and the axle in order to assure a proper driveline
angle. If this is not done, major problems will soon become apparent with
vibrations, u-joint failure, bearing failure, etc. The angle of the
driveline must be the same whether the truck is static or is loaded to its
capacity, which can be several tons. The constant alignment is
accomplished by the means of an "automatic leveling valve". When
weight is added to the truck, the automatic leveling valve senses the change in
height adds air to the air springs in order to maintain the proper height and it
lets air out when the weight is removed. The suspension system on a MDT is
designed to work best at approximately 90% to 100% of its designed weight
capacity. So when the truck is loaded it will ride somewhat better than
when it is empty. However, because the suspension is designed for
maintaining the proper height, the ride quality is very secondary. Unlike
a light duty vehicle, where the primary concern is the ride quality. When
you hit a bump with a MDT the tire if properly inflated will still absorb
approximately 25% of the BUMP. In order for the air spring to absorb
the BUMP, the walls of the air spring must flex or stretch to allow someplace
for the BUMP to go. The more capacity the air spring has to carry weight, the
heavier the construction is, which makes it less flexible to absorb the BUMP.
Another way the air spring can absorb the BUMP is to have the air exit the air
spring when a BUMP occurs. One thought to achieve this is to install a ping
tank. In its simplest form it is an expansion tank piped to the air
springs, which gives more air capacity to the air springs. When the air
spring can't flex to dissipate the BUMP, the BUMP transmits into the frame of
the truck and all components attached to the truck, such as your 5th wheel and
you the passenger. When it comes to the passengers, what do we do?
We install AIR RIDE SEATS so we do not have to absorb the BUMP with our
body. By installing an air suspension hitch for the 5th wheel,
we now have a means of absorbing the BUMP before it gets to the trailer.
When the BUMP travels up to the air springs on the hitch, the air springs expand
or stretch because they are sized small enough to be able to flex easily.
If we don't put the absorbing means under the pin of the trailer, its frame and
pin box must absorb the BUMP. This again is added stress and fatigue that
is not designed into the trailer. We all know it takes time for stress and
fatigue to show up as breakage. So if you think you do not have a problem
with your trailer's ride just because the TV stays in place, isn't necessarily
true.
Remember, when your truck rides too rough you cannot just remove air from the air springs on your truck thinking it will give you a softer ride. What it will do is it will change your driveline angle and cause you more problems…problems you do not want. So the proper way to solve the hard ride your trailer is getting is to install an air suspension system between your truck bed and your 5th wheel trailer and in this case it’s an air suspension hitch, as it will prevent damage to your 5th wheel RV.
Copyright ©1999, 2000, 2002 Jerry L. Clark
AIR SUSPENSION HITCHES--------ARE THEY ALL ALIKE ???
I feel that anytime one is going to spend in excess of $2000.00 on anything some research should be done to make sure that you get the best value for your dollar. If more than one company manufactures a product, you can be assured that there are some differences in the same product even though they both are intended to do the same task. The same is true with air suspension hitches. There are currently three designs on the market; vertical lift, angle beam and level beam.
In a vertical lift design, the action of the hitch head is in a vertical movement only, which is the only way you want the head to move. There are a couple of ways to allow the head to move in a vertical movement. One is to design the hitch so the mechanism, which captures the head, rides up and down on ball/roller bearings. At first glance this may sound like a good idea. But, with this kind of design the framework must be extremely rigid and probably have several gussets (braces) attached to it. But more importantly, the purpose of a bearing is to reduce friction. It does this by rolling on case hardened rollers or balls in a lubricant. A bearing is not designed for rapid changes of direction. When this happens, the rollers will start to skid instead of roll. It will not be long before the bearing action is no longer operating as it was designed to do. The proper way to design a vertical lift hitch is to use high strength 80,000 lb. bronze bushings and install them over chrome shafts. The bronze bushing does not know which direction they are traveling and as long as there is grease in them they should last several years. A personal note on this design; when I designed our first vertical lift hitch we used the bronze bushing design and a customer purchased the one I was using from me while it was on my truck. Before I gave him delivery of it I removed the pillow blocks containing the bushings and measured them for wear. I had in excess of 10,000 towing miles on the hitch at the time. There was less than .001" of wear on the bushings and the chrome shafts. The reason we designed the vertical hitch was because we had a very small "foot print" to fit into some of the really small "wells" that are in a few of the trucks. The reason we stopped making it was because there was a lot of machining of parts and was very labor intensive to manufacture. During the time we were selling them I did reserve patent rights for them so I can continue to manufacture them in the future if need be.
The next design is one called the "angle beam". A beam design is very simple and has been around since there has been wood. One end of the beam is attached to the air springs, the other end is attached to the frame of the hitch with some sort of attachment, which allows the beam to rotate when the air springs are inflated and deflated. The hitch head is secured some place between the two points of attachment. The amount of pin weight that is transferred to the hinge end of the beam is in direct relation to the distance from the hitch head to the hinge point. The closer the head is to the hinge point, the more weight that is transferred. This is true on any kind of beam design. An angle beam design talks of the location of the hinge point in relation to the hitch head. Two things need to be taken into consideration here. The greater the distance the hitch head is above the hinge point and the closer the head is to the hinge point will result in the head having more forward travel when the air springs are inflated or when the hitch moves upward. We know from experience that when the head is elevated to a point approximately 8" above the hinge point and there is a distance of 23" between the hitch head and the hinge point the head will travel forward 2". When the head travels forward the 2" on the upward movement of the hitch, it must also travel backward the 2" when the hitch returns to its running height. What is actually happening is the hitch is pulling your trailer forward 2" on the upward movement of the hitch and then pushing your trailer backward 2" on the down travel of the hitch which causes a surging sensation in your tow vehicle. This action takes place when the hitch is fastened solid to the bed of your truck. There is another angle beam design hitch on the market where the hitch head actually moves to try to compensate for the forward and aft travel of this kind of design. That will be another article, as room does not permit at this time.
The other design of hitch is the "level beam" design. The attachment points of the hitch head, pivot points and air springs are the same as for the angle beam design. The end goal is to have a "beam" design hitch work the same way as a vertical lift hitch works; have the hitch head go only straight up and down. When the head goes straight up and down it is impossible to get any surging in your tow vehicle. We knew with the angle beam design that was impossible to achieve, so we set out to solve that problem and the result was the level beam design. In a nutshell what that means is when the hitch head is in its operating position, it is level with the axis point of the beam. This design allows for the head to move upward 4" while traveling forward only 1/8". This very small forward travel cannot be felt in the tow vehicle. Because this design has never been used on an air suspension hitch, I have applied for a US Patent for its design.
Hopefully you have an understanding of the different designs available and how they work. There is another point that I think is important when it comes to getting your monies worth when purchasing an air suspension hitch. That is knowing that the hitch you purchase will do what you were told it would do, also known as the Gross Trailer Weight Rating. As of this writing, all the companies manufacturing RV 5th wheel air suspension hitches have NOT had their hitch framework tested by an independent testing facility with one exception. However, all of the companies are rating their hitch framework the same as the hitch head they are using is rated. The current companies supplying hitch heads are Pull-Rite 25,500 lbs, Reese 22,000 lbs, and Holland 32,000 lbs. To get a hitch tested by an independent testing facility takes a lot of time and money. However, it is the only way to know that the hitch will withstand the rating that is put on it. The one exception to having the testing done is the TrailerSaver Air Suspension Hitch. On October 4, 1999 General Testing Laboratories, Inc. performed the testing on the TrailerSaver Air Suspension Hitch according to Wisconsin Department of Transportation guidelines. One of the guidelines is that the hitch must be tested in a compression and tension mode at 30% over its intended rating. This meant that in order for the hitch to be rated at 32,000 lbs. it had to pass the test in both modes at 41,600 lbs. It did pass with out any breakage and the results of that test are published on the Internet at www.trailersaver.com if you wish to read them. There are several other topics to be discussed regarding air suspension hitches such as movement dampening, construction procedures, fabrication techniques, etc, which will have to be covered in another article.
Information contained in this article is not only of my own beliefs but that of professional engineers and metal workers.
COMPARE THE DIFFERENCE
of FORWARD TRAVEL
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This drawing demonstrates the differences of forward travel in direct relation to vertical lift between the TrailerSaver Air Suspension Hitch Level Beam design, and the Angle Beam design on the bottom.Notice the locations of the pivot points on the two models. |
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TrailerSaver Model TSLB (Design known as Level Beam) Model "AB" (Design known as Angular Beam)You will notice by the arc of each hitch, that the TrailerSaver hitch moves forward only 1/8" at it’s full lift of 4". On the Model AB design you will see by the arc that at 4" of up lift the hitch has traveled forward 2". When this happens, the trailer is pulled forward the 2" on the up lift and then pushed backward the 2" on the down travel. This causes a surging action in the tow vehicle, and also puts added stress on the kingpin and pin box of the trailer.Copyright © 1999, 2000, 2001 Jerry L. Clark |
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FEATURES |
TRAILER SAVER |
D SQUARE |
MOUNTAIN
MASTER |
| Tested by an Accredited Testing Facility | YES | NO | NO |
|
Accredited Rated Towing Capacity |
32000 lbs. | Not Accredited | Not Accredited |
|
Pin Weight Capacity, Lbs. |
5000 & 7500 | 5000/12000 | INA |
| Hitch Head Manufacturer | Holland 32K | Pull-Rite/Holland | Holland 32K |
| 4-Way Hitch Head Movement | YES | YES | YES |
| Minimum to Maximum Operating Height | 10.5" to 14.5" | 13.0" to 15.5" | INA |
| Forward Head Travel @ Max. Lift | 1/8" | 1.5" | INA |
| Lifting Design | Level Beam | Angular Beam | Angular Beam |
| Front of Hitch to Kingpin C/L | 21" | 24" | INA |
| Dimensions L x W | 32" X 23" ** | 36" X 24" | INA |
| Air Springs Manufacturer | Good Year | Firestone | INA |
| Manufactures Written Warranty | 3 Years | None | None |
| Approximate Shipping Weight , LBS. | 350 | 170 | 165 |
| Push on Air Line Fittings | YES | YES | NO |
| Push Button Control W/Pressure Gauge | YES | YES | NO |
| Completed Products Liability Insurance Coverage | YES | INA | NO |
| 3 Coat Industrial Paint System | YES | NO | NO |
| Goose Neck Adaptable | YES | INA | NO |
| Heavy Duty Construction | YES | NO | NO |
| Jig Welded | YES | INA | INA |
| Computer Controlled Manufacturing | YES | NO | NO |
| Certified Welders | YES | INA | INA |
| Safety Stops Applied | YES | YES | YES |
| Dealers & Installers Organization | YES | NO | NO |
| Climate Controlled Mfg. Facility | YES | NO | INA |
| Lubrication Fittings Installed | YES | YES | YES |
| Shipped Fully Assembled | YES | YES | INA |
** Model
TSLB1BH is 32"x18.5"
All the information complied above is, to the best of our knowledge, accurate at
the time of publishing.
It is possible that specifications may change from time to time without our
knowledge.